Use a precise target type for Beacon requests.

Source/core/loader/BeaconLoader.cpp

Index: Source/core/loader/BeaconLoader.cpp
diff --git a/Source/core/loader/BeaconLoader.cpp b/Source/core/loader/BeaconLoader.cpp
index 7773528991bc5790ba422e45667ad2c4bcda7bd3..3f4b81a109ed08030f0007c5ae2c94ce717cd136 100644
--- a/Source/core/loader/BeaconLoader.cpp
+++ b/Source/core/loader/BeaconLoader.cpp
@@ -21,8 +21,7 @@ namespace blink {
 
 void BeaconLoader::prepareRequest(LocalFrame* frame, ResourceRequest& request)
 {
-    // NOTE: do not distinguish Beacon by target type.
-    request.setRequestContext(blink::WebURLRequest::RequestContextPing);

[Mike West, 2014/08/13 13:54:41]

Why was this note here? It's certainly less relevant now that we've removed the
TargetType enum, but was there a good reason for its being there in the first
place?

[sof, 2014/08/13 14:05:38]

Just a remark that Blink didn't expose the "Beacon-ness" of the request, as
there was no known need for doing so.

It would have been better if that went hand-in-hand with not defining
RequestContextBeacon, as it wasn't being used. But no longer an issue.

+    request.setRequestContext(WebURLRequest::RequestContextBeacon);
     request.setHTTPMethod("POST");
     request.setHTTPHeaderField("Cache-Control", "max-age=0");
     request.setAllowStoredCredentials(true);